Playing 3.5 hr matches on slow clay is harder on the body than a 2hr matches on a rubberised hard court.

One of the reasons why Tennis Australia abandoned the rubberised Rebound Ace was the ridiculously high number of injuries that the surface caused, with many players rolling their ankles on it year after year. Players were complaining that their feet were still hurting for numerous days after the tournament finished.

Clay is much softer and easier on the joints than hard courts. That is why many older players in the US prefer to play on har-tru than hard courts, even if it doesn't suit their game as much.

And most of the hard courts used nowadays are slow, and a typical slow hard court match with long, gruelling rallies is going to give the body a far bigger pounding than a typical clay court match.

Quote:

If the whole season was slow clay Nadal would still have developed the knee issues he has now. Notice how his knee issued typically flare up at the end of the clay court season and not the hard court swings?

No-one in their right mind thinks that the whole season should be slow clay

Nadal himself like many other players has wanted there to be many more grass court events, which would be ideal, but as we know that is not financially feasible.